1. Field of the Invention
This invention relates to apparatus used to detect animal estrus, and more particularly to such apparatus which is adapted to be worn externally by a first animal and is pressure actuated by a second animal mounting the first animal.
2. Description of the Prior Art
In the field of animal husbandry, mankind is continually seeking to improve his livestock by the selective breeding thereof. However, such breeding entails determination of when estrus is occurring in the livestock so that, to the greatest extent possible, the livestock can be impregnated through the selective utilization of the preferred source of natural or artificial insemination.
As is known, estrus is characterized by an increase in the mucus present in the vaginal canal of an animal. Thus, prior art patents such as U.S. Pat. No. 3,297,020 granted Jan. 10, 1967, to Mathiesen, and U.S. Pat. No. 3,844,276 granted Oct. 29, 1974, to McDougall, disclose apparatus which includes a probe insertable into the vaginal canal for detecting either an increase in current flow through the mucus or a decrease in the resistance of the mucus, respectively, which indicates the animal is in estrus.
As is also known, when estrus occurs in livestock, such as a cow for example, the cow will show an increased tendency to stand and permit itself to be mounted by other animals. When the mounted animal allows the mounting animal to remain for about five seconds, a "standing mount" has occurred. The most frequent mountings occur, of course, by bulls, but mountings are also made by other cows. Accordingly, the repeated mounting of a cow by any other such animal is a good indication that it is in estrus. The occurrence of a number of "standing mounts" indicates true estrus and the optimum time for artificial insemination is immediately following occurrence of the fifth standing mount, according to experts in the field. The time elapsed since the fifth standing mount is grossly indicative of the number of artificial insemination ampules required to ensure fertilization of the cow.
Although throughout this application a cow is used as an example, it is to be understood that the present invention may be easily adapted to be used to detect estrus in other animals such as horses, sheep, goats, swine, etc.
Some of the prior art patents, such as U.S. Pat. No. 3,842,802, granted Oct. 22, 1974, to Lang et al., and U.S. Pat. No. 3,824,989, granted July 23, 1974. to Horner et al., take advantage of the aforesaid behavior by attaching to the bull's head or neck a harness which carries a marking device arranged to mark the cow when the bull mounts the cow, thereby indicating the presence of estrus in that cow. However, such devices suffer from the drawbacks that they are relatively expensive and complicated. In addition, it would appear that they are not too useful for selective breeding purposes since the marking animal, the bull, has likely already inseminated the cow in the process of marking it unless the bull has been surgically rendered incapable of inseminating the cow.
U.S. Pat. No. 3,844,273, granted Oct. 29, 1974, to Polson discloses an apparatus which includes a battery operated radio transmitter worn by each cow. The transmitter is turned on when the cow is mounted by another animal, thereby indicating the presence of estrus to the animal breeder who may then locate the cow by utilizing a radio direction finder. Polson also discloses electrical means to measure the amount of time elapsed since the radio transmitter is turned on. However, the Polson apparatus suffers from the drawbacks of being relatively expensive, hard to repair, and having a relatively limited range. In addition, it would seem that the Polson apparatus would be subject to being unable to perform its intended function relatively frequently in the event that batteries become old and fail or in the event the batteries become discharged after the transmitter has been activated for a period of time before the animal breeder can locate that particular cow. Further, it indicates only that at least one mount has occurred and does not indicate the number of mounts or the length of any.
U.S. Pat. No. 3,076,431, granted Feb. 5, 1963, to Rule et al., and Canadian counterpart application Ser. No. 682,861, granted Mar. 24, 1964, disclose a pressure activated, hydraulic type of estrus detection device which is secured to the rump of a cow. This device is in the form of a long tube divided into two interconnected compartments, one compartment being soft walled and partially filled with a colored fluid, while the other compartment has collapse resistant walls and includes an aperture leading to an absorbent material which surrounds the tube. Pressure on the device caused by another animal forces the colored fluid into the collapse resistant compartment and thence into the absorbent material, thereby indicating the presence of estrus. The time taken to fill the collapse resistant compartment with fluid is alleged in the Rule patent to act as a mechanism whereby short applications of pressure on the tube will not give an observable indication of colored fluid on the absorbent material, although applicant doubts the consistant operability of this aspect of the Rule disclosure. However, as will be seen, the Rule device utilizes a construction and operating principle quite different from that disclosed by applicant. Further, it does not count the mounts and does require close observation of the animal's rump area.